Condensed Consolidated Statements of Cash Flows (Unaudited) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Cash flows from operating activities:
Net loss	$ (12,112)	$ (26,849)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation and amortization including right-of-use assets	307	107
Impairment of acquired IPR&D		21,692
Changes in fair value of financial instruments	77	96
Change in fair value of contingent consideration	133	(134)
Noncash interest (income) / expense	(4)	35
Foreign currency loss	59	61
Amortization of debt issuance costs	147	109
Accretion on discount to short-term investments	(342)	(138)
Stock-based compensation	1,000	412
Benefit for deferred taxes		(4,555)
Changes in operating assets and liabilities:
Prepaid expenses and other current assets	69	54
Non-current assets	(953)
Accounts payable and accrued expenses and other current liabilities	953	(554)
Long-term liabilities	(193)	(7)
Net cash used in operating activities	(10,859)	(9,671)
Cash flows from investing activities:
Purchase of property and equipment	(96)	(19)
Purchase of available-for-sale securities, net	(46,035)	(15,891)
Maturities of available-for-sale securities	42,800	25,300
Sale of available-for-sale securities, net	10,651
Net cash provided by investing activities	7,320	9,390
Cash flows from financing activities:
Issuance of common stock upon exercise of warrants		18
Issuance of common stock upon at the market offerings, net	4,890	493
Proceeds from exercise of stock options	6	3
Capital lease obligation principal payments		(243)
Net cash provided by financing activities	4,896	271
Effect of exchange rate changes on cash and cash equivalents	13	11
Increase in cash and cash equivalents	1,370	1
Cash and cash equivalents beginning of period	24,301	22,121
Cash and cash equivalents end of period	25,671	22,122
Supplemental disclosure of cash flow information:
Cash paid for interest	$ 528	$ 334